SHOULD WE SCREEN MALES AND FEMALES DIFFERENTLY FOR COLORECTAL CANCER? A COST-EFFECTIVENESS ANALYSIS

Background
Most colorectal cancer (CRC) screening programs use a uniform screening strategy. However, it may be more efficient to screen males and females differently due to (ambivalent) biological and demographic differences between the sexes. For example, males are known to have higher Hemoglobin concentrations in their stool and a higher prevalence of advanced colorectal neoplasia, leading to a higher positivity rate for fecal immunochemical testing (FIT). At the same time, females have a higher life expectancy than males, which is why they may benefit more from screening at older ages. We investigated the cost-effectiveness of several sex-specific CRC screening strategies.

Methods
The MISCAN-Colon microsimulation model was used to simulate CRC screening for males and females separately while varying four parameters: screening interval (1, 2 or 3 years), FIT positivity cut-off (15, 20, 30, 40, 47, 50 or 60 microgram Hemoglobin per gram feces [µg Hb/g]), starting age (50, 52, 54, 55, 56, 58 or 60 years) and stopping age (70, 72, 74, 75, 76, 78 or 80 years). This resulted in 1029 screening strategies per sex. For each of these strategies, quality-adjusted life-years (QALYs) gained, costs and colonoscopy demand were calculated. Efficient screening strategies, i.e. strategies that provide the best value for money, were identified for a scenario with and without colonoscopy capacity restrictions. We assumed a willingness-to-pay threshold of 20,000 EUR per QALY gained throughout.

Results
When colonoscopy capacity was unlimited, most of the efficient strategies had the lowest FIT cut-off considered, i.e. a cut-off of 15 µg Hb/g, and stopping age 80 (Figure). The cheapest efficient strategies had a screening interval of three years starting at age 60, whereas the costliest strategies had an interval of one year starting at age 50. Screening strategies for males and females were similar. Costs and effects of efficient strategies ranged from 198 QALYs gained and cost-saving to 435 QALYs gained at €603,197 per 1,000 simulated males and 1,000 simulated females combined. The optimal screening strategy comprised annual screening at a FIT positivity cut-off of 15 µg Hb/g for ages 50 through 80 for both sexes. When colonoscopy capacity was restricted to 20% extra capacity compared to what is currently required for the Dutch screening program, efficient strategies had a higher FIT positivity cut-off and stopping age for males compared to females.

Conclusion
From a cost-effectiveness perspective, it is not recommended to stratify CRC screening by sex if colonoscopy capacity is unlimited. However, if the capacity is restricted, more intensive screening at a higher FIT positivity cut-off is recommended for males.